This invention relates to the field of air lubricated boat or ship hulls used as means to increase the efficiencies of such hulls and to their propulsion and stabilization systems.
The idea of placing a layer of air between the underside of a ship""s hull and its supporting water surface has been around for many years. The Russians have reported some success with this concept. FIGS. 25 through 32 of this application show some of the more recent thinking along the line for Air Lubricated Ship designs. These are normally referred to in the specifications herein as the ALS.
Further, applicant has realized some commercial success with his pressurized air supported boat designs. One of these is illustrated in U.S. Pat. No. 5,839,384. That patent illustrates a boat hull where the bow of the boat operates proximal the water surface. The pressurized air cushion in a cavity built into an underside of the boat""s hull depresses the water surface going from the bow to the stern such that the stern is lower than the bow. The pressure in the air cushion is essentially constant over the entire area of the air cushion. Air cushioned boats of this general type are commonly known as Surface Effect Craft, or simply SES""s, since they work on the water""s surface.
There is a major difference between the ALS and the SES concepts. The forward portion of the ALS is below the water surface and creates a hole in the water. Proper location of a step in the hull and shaping of the aft sections of the hull of the ALS form a cavity when the ALS is moving forward. This effect can be realized by viewing the rising of the water behind a planing boat""s hull until it reaches sea level.
An example of current thinking in ALS hull design can be seen in FIGS. 27 and 31 and 32 of this application. Blower pressurized air is supplied to the cavity formed behind the step in the hull thereby creating a pressurized air layer between portions of the bottom of the ship and the supporting water surface. This, of course, reduces wetted area friction of the hull. It is to be noted that the air cavity rises going from aft of the step rearward until the water surface again contacts the hull. Efficiency gains for the ALS compared to a conventional hull are claimed to be in the twenty-percent area. Power to run the blower is very small with a rough estimate as five percent or less of propulsive power claimed.
By contrast, the SES is more of a surface-skimmer type vessel whereby a blower-pressurized air cushion disposed below the SES""s hull supports a majority, normally about eighty percent, of vessel weight. The SES""s bow is located proximal the water surface and the effect of the pressure in the air cushion is to depress the water level going from bow to stern. This makes for a very efficient vessel that requires only about half of the propulsive power of a comparable monohull or catamaran at high speeds. However, as size and weight of the SES increase the percentage of total power required to run the blower(s) increases rather dramatically. Roughly speaking, blower power requirements, given as a percentage of the propulsive power requirements, range from about ten percent for a 100 foot (30-meter) SES to more than fifty percent for a 656 foot (200-meter) SES. Larger size SES""s have greater proportional blower power requirements. As a point to consider, a 100-foot (30-meter) SES would normally depress the water going from bow to stern by about two feet (0.61 meter) while a 656 foot (200-meter) SES would depress the water going from bow to stern by about 16 feet. That is eight times as much for the large SES.
In rough comparison: 1) The ALS gives about a twenty percent reduction in propulsive power requirements and needs about an additional five or less percent power for its blowers and 2) The SES generally gives about a fifty percent reduction in propulsive power requirements but needs from ten to over fifty percent additional power for its blowers. The SES clearly wins the overall efficiency battle for smaller sizesxe2x80x94say up to 350 feet (107 meters) or so. The ALS comes into primary contention for large hulls where its need for blower power of only about five or less percent of the value of its propulsive power overcomes its lower hull efficiency. A heavily loaded 656-foot (200-meter) SES would normally require on the order of fifty percent of its propulsive power to drive its blowers.
This instant application presents significant improvements to ALS technology as applied to all type and sizes of boats and ships but is primarily directed toward large ships. Some areas of advancement to the ALS concept offered by the instant invention include: 1) Means to extend the ALS""s air cavity further forward, sometimes with multiple air cavities, and thereby further reduce hull wetted area friction, 2) Hydrofoil(s) disposed forward in the ALS""s hull to both increase hull stability and to provide means to extend the air cushion further forward in the ALS""s hull, 3) Propulsion systems particularly conceived and disposed to maximum their efficiency in ALS""s, and 4) Means to stabilize the ALS by addition of outrigger hulls. The instant invention presents both single and multiple ALS hull configurations.
The instant invention offers advancements over applicant""s earlier inventions as well as over the prior art. These advancements are discussed in some detail in the following sections.
Szpytman, U.S. Pat. No. 3,871,317; Dunajeff, U.S. Pat. No. 1,412,846; Meyer, Jr., U.S. Pat. No. 3,968,762; Tattersall, U.S. Pat. No. 4,166,515; Huang, U.S. Pat. No. 5,339,761; and Schlichthorst et al, U.S. Pat. No. 4,660,492 all present partially air cushion supported marine craft that also have hydrofoils. As air cushioned craft that utilize pressurized air to depress the water surface below their air cushions as seen going from the bow to the stern, these craft are known as Surface Effect Ships (SESs). None of these craft have hydrofoil members that emanate from either side of a lower part of the forward bow portion to thus form an enlarged substantially horizontal surface on the underside of the forward bow portion as compared to bow sections proximal to and above the hydrofoil as does the instant invention. The aforementioned substantially horizontal and wide under surface at the bow that is formed by the design and placement of the bow hydrofoil provides good ride qualities since the bow is deeply submerged and also provides a wide substantially horizontal surface that allows starting an air cushion proximal the bow. It is further to be noted that all of the aforementioned U.S. Patents are SES type pressurized air cushion designs that have their bows at or very close to the water surface. The pressure of the blower supplied air depresses the water surface going from forward to aft so that the water surface is substantially lower at the stern than at the bow. The instant invention is a true Air Lubricated Ship (ALS) since its bow is deeply submerged to actually dig a deep hole in the water. The water leaving the bow at the step that starts the air cushion(s) rises going aft. While not quite as efficient as a pure SES, the advantage of the instant invention""s ALS concept is that a much lesser amount of blower pressurized air and hence blower power is required to supply the air layer(s).
The primary object of the instant invention is to offer a notable improvement in ALS efficiency by extending the pressurized air lubrication layer(s) further forward in the ALS""s hull.
A related object of the invention is that the air or gas layers be pressurized by artificial means.
A directly related object of the invention is to provide a hydrofoil forward on the ALS that, due to its widening effect on lower portions of the ALS""s hull, allows a step that defines the forward end of the first air lubrication layer to be moved further forward.
It is a related object of the invention that the a step be positioned at a forward portion of the air layer(s) to direct water away from the ALS""s hull aft of said step.
It is another related object of the invention that a lower surface proximal to and forward of said step(s) turn downward to direct water flow downward when the improved air lubricated ship is moving forward.
It is a further related object of the invention that said pressurized air or gas layer(s), on average, slop upward aft of step(s).
Yet another object of the invention is that the hydrofoil include flap-like members that aid in controlling pitch and roll of said ALS.
It is a further object of the invention that an underwater section of the improved ALS""s hull, as seen in a horizontal plane taken above the hydrofoil when the improved air lubricated ship is moving forward, is at least partially air foil shaped over its forward portion to thereby reduce drag of the hull.
It is a yet another object of the invention that a lowermost submerged portion of the ALS proximal a bow of the ALS be within twenty percent of the submerged depth of a lowermost portion proximal of an aft portion of said improved ALS when the ALS is moving forward in a calm sea.
It is another object of the invention that a lowermost submerged portion of the ALS proximal a bow of the ALS be within twenty-five percent of the submerged depth of a lowermost portion proximal of an aft portion of said improved ALS when the ALS is moving forward in a calm sea.
It is a further object of the invention that a lowermost submerged portion of the ALS proximal a bow of the ALS be within thirty percent of the submerged depth of a lowermost portion proximal of an aft portion of said improved ALS when the ALS is moving forward in a calm sea.
It is a yet a further object of the invention that a lowermost submerged portion of the ALS proximal a bow of the ALS be within thirty-five percent of the submerged depth of a lowermost portion proximal of an aft portion of said improved ALS when the ALS is moving forward in a calm sea.
It is still another object of the invention that a first step forward of a first gas layer be disposed, at least in its majority, in a forward fifteen percent of a length of said improved ALS.
It is yet another object of the invention that a first step forward of a first gas layer be disposed, at least in its majority, in a forward twenty percent of a length of said improved ALS.
It is a further object of the invention that a first step forward of a first gas layer be disposed, at least in its majority, in a forward twenty-five percent of a length of said improved ALS.
It is still another object of the invention that a first step forward of a first gas layer be disposed, at least in its majority, in a forward thirty percent of a length of said improved ALS.
It is a further object of the invention that the first gas layer be bordered over at least a majority of its length by sidekeels.
It yet another object of the invention that it further includes a second step in the underside of said ALS wherein said second step is disposed, at least in its majority, proximal an aft end of said first pressurized gas layer and wherein a second pressurized gas layer is disposed, at least in its majority, aft of said second step.
It is a directly related object of the invention that said second pressurized gas layer, on average, slopes upward going from forward to aft.
It is yet another object of the invention that the second gas layer be bordered over at least a majority of its length by sidekeels.
It is a further object of the invention it may also include a third step in the underside of the ALS wherein said third step is disposed, at least in its majority, proximal an aft end of said second pressurized gas layer and where a third pressurized gas layer is disposed, at least in its majority, aft of said third step.
It is a related object of the invention that the third pressurized gas layer, on average, slopes upward going from forward to aft.
It is a further related object of the invention that the third gas layer may be bordered over at least a majority of its length by sidekeels.
It is a related object of the invention that the external surfaces of sidekeels bordering any or all of the gas layers, as seen in a vertical transverse plane of the ALS, may be curvilinear over a majority of their lower surfaces.
It is a directly related object of the invention that the external surfaces of the sidekeels bordering any or all of the gas layers, as seen in a vertical transverse plane of the ALS, may be of circular arc sections over a majority of their lower surfaces.
It is yet another object of the invention that sidekeels bordering one or more gas layers may be continuous on either side of the gas layers.
It is a further object of the invention that separate artificial gas pressurization means may be used to pressurize any of the gas layers.
It is an optional object of the invention that the same artificial gas pressurization means may be used to pressurize two or more gas layers.
It is a further optional object of the invention that downward extending gas restraining seal(s) may be placed proximal an aft end of one or more of the gas layer(s).
It is a directly related object of the invention that said downward extending gas restraining seal(s), as seen in vertical transverse plane(s) of the instant invention ALS, can be angled to horizontal over a majority of their width.
It is a further object of the invention that outrigger hulls can be disposed either side of a main hull of said air lubricated ship.
It is a directly related object of the invention that said outrigger hulls can be retractable.
It is another directly related object of the invention that said outrigger hulls can be retractable downward such that a portion of at least one of the outrigger hulls is disposed below one of the sidekeels of said improved air lubricated ship.
It is yet another object of the invention that propulsors are preferably disposed proximal an aft end of said sidekeels.
It is a related object of the invention that the propulsors are waterjets that take in inlet water from a portion of a periphery of said sidekeels.
It is a further related object of the invention that one or more air fences can be disposed above and proximal to water inlets of said waterjets whereby said air fences restrict air from flowing downward into the waterjet""s water inlets.
It is a further optional object of the invention that said propulsors can be propellers with said propellers rotating, as seen in an aft view of the improved air lubricated ship, with an upper blade rotating in an outboard direction to thereby aid in restricting gas leakage from an aft gas layer by building up a pressure front of water over an aft end of said aft gas layer.
It is a further optional object of the instant invention that multiple hull ALSs to the instant invention configuration be offered.